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USSD-Based Decentralized Finance on Rootstock

This guide introduces a novel integration architecture that connects legacy GSM feature phones to the Rootstock (RSK) blockchain network via USSD (Unstructured Supplementary Service Data). The system enables decentralized financial services , including P2P transfers and micro-loans, for users who have no smartphone or internet access.

참고

USSD is a real-time communication protocol built into every GSM network globally. It works on any mobile phone, requires no internet, no app installation, and no data plan , making it one of the most accessible communication channels in the world.

Why This Matters

Web3 services today are gated behind smartphones and internet connectivity. In large parts of Africa, South Asia, and Latin America, hundreds of millions of people still rely on basic feature phones for communication. This creates a direct contradiction blockchain promises financial inclusion, but its interfaces exclude the very populations who need it most.

This architecture removes that barrier. By routing USSD sessions through an off-chain relay server that communicates with the RSK network, any person with a basic GSM phone and a SIM card can:

• Check their on-chain token balance
• Send peer-to-peer transfers to other wallet addresses
• Request micro-loans from a smart contract

Who This Is For

This documentation targets developers who want to build financial inclusion tools on Rootstock. You should have a working understanding of:

• Solidity and smart contract deployment on RSK
• Node.js backend development
• Basic telecom concepts (USSD session flow)

System At a Glance

The solution is composed of three layers that work together:

1. The User Layer — A feature phone initiates a USSD session by dialing a shortcode (e.g., *384#). All interaction happens through a menu-driven text interface.

2. The Off-Chain Relay Layer — A Node.js Express server receives the USSD payload from a telecom gateway (such as Africa's Talking), interprets the user's menu choices, and constructs the appropriate blockchain transaction or read call.

3. The On-Chain Layer — A Solidity smart contract deployed on the RSK Testnet handles balances, P2P transfers, and micro-loan logic. The relay server acts as a funded relayer wallet, signing and broadcasting transactions on behalf of the user.